ARM: S5P: Add PMU device

This patch adds an initcall for the s5p platforms so that they register
their PMU IRQs with the PMU framework in the Kernel.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>